Converting a string to a double when it includes symbols (in nonlinear inequality solving)

First of all, the nonlinear inequality constraints page is here: Nonlinear inequality constraints. Please go have a look at defining c in Step 2 to understand my problem properly.

In Step 2, one must define a list of constraints called "c". I intend to be solving nonlinear inequalities in a loop, and am therefore getting the computer to write the constraint list for me as a string. Say my constraint list (outside of confun.m) is

constraint = '[1.5 + x(1)*x(2) - x(1) - x(2);-x(1)*x(2) - 10]'

so that class(constraint) = char . I attempt to pass it to confun.m as c = constraint, it tells me it requires it to be of type double. This is fair. When I attempt to pass it as c = str2num(constraint), it makes c = [], because presumably it cannot understand the x's. And c = str2double(constraint) produces c = NaN. I have also tried various combinations of things using syms and eval, to no end. How do I do this in the right way?

Thank you!

Answer 1

[Bianca De Sanctis]

Got it. c = eval(constraints) worked. I had been trying weird combos of eval, but not alone.